This research proposal deals with the study of hemoglobin synthesis in sickle cell anemia and thalassemia, and will be concentrated in 3 major areas: (1) To refine a technique for the prenatal diagnosis of sickle cell anemia and thalassemia by study of hemoglobin synthesis in cord blood of fetus. (2) To define the nature of the molecular defect in beta thalassemia by hybridization experiments using radioactive DNA prepared by reverse transcriptase. (3) To study the mechanism of production of Hemoglobin Constant Spring by a cell free system, and a search for suppressor tRNA.